Improved motor sledge

ABSTRACT

In a motor sledge having a supplementary frame extending from the rear end of the frame construction and flexibly pivoting around a horizontal axis the slackening of the common drive belts due to upward movement of the supplementary frame is prevented by a pair of rolls freely rotatable above the point of pivotement. When the supplementary frame pivots upwardly the upper surface of the drive belts are pressed against the rolls.

United States Patent Pollanen [54] IMPROVED MOTOR SLEDGE Kyosti JohannesPollanen, Isokyla,

[72] Inventor:

Finland [73] Assignee: Velsa 0y, Kurikka, Finland [22] Filed: April 26,1971 [21] Appl. No.: 137,477

[30] Foreign Application Priority Data April 27, 1970 Finland ..l 168[52] US. Cl ..,..l80/5 R, 180/954, 305/20, l 305/27 [51] Int. Cl ..B62m27/02, B62d 55/16 [58] Field of Search....305/20, 27, 10; 180/924, 9.2,180/954, 9.32

[56] References Cited UNITED STATES PATENTS 3,157,913 11/1964 Habert .L'"ISO/9.24 R

[ Sept. 19, 1972 3,447,621 6/1969 Schoonover ..l80/9.64 R

FOREIGN PATENTS OR APPLICATIONS 842,862 3/1939 France ..305/22 PrimaryExaminer-Richard J. Johnson Attorney-Albert M. Parker 57 ABSTRACT ln amotor sledge having a supplementary frame extending from the rear end ofthe frame construction and flexibly pivoting around a horizontal axisthe slackening of the common drive belts due to upward movement of thesupplementary frame is prevented by a pair of rolls freely rotatableabove the point of pivotement. When the supplementary frame pivotsupwardly the upper surface of the drive belts are pressed against therolls.

2 Claims, 3 Drawing Figures PATENTEDszmmz 3,692 132 SHEEI 3 0F 3 r W (mma! BACKGROUND OF THE INVENTION 1. Field of the Invention The inventionrelates to the field of motor sledges having a supplementary frame.

2. Description of the Prior Art The disadvantage of fixed frameextensions is that on rough ground the front part of the sledge tends todive into the slop when going uphill. Also, the steerability of a sledgewith such a fixed extension frame is not good owing to the length andstiffness of the frame. In spite of the lengthened drive belt thepulling efficiency is not entirely desirable, since on uneven groundeach part of the roller belt will not touch the ground with the samesurface pressure. On hard, rough ground the long stiff frame has tendedto brake under a slightly heavy driver. Furthermore, the desireddecrease of the surface pressure of the roller belt against the groundhas not been obtained in spite of the longer bearing surface, since it'has been necessary to support the extension frame with many kinds ofsupporting structures to reinforce the joint, and these structures haveadded to theweight of the extension part.

There are also different previously known snowvehicles in which thedrive belt has been fitted around sprung roller wheels. It has beennoted, however, that the part of the belt above the wheels in theseknown structures will slacken, in which case the grip between r theroller belt and the wheels weakens decisively.

SUMMARY OF THE INVENTION According to the invention there is provided animproved motor sledge having a hinged frame extension and limitingorgans fitted against the upper surface of the drive belt and attachedto the frameapproximately above the joint to prevent the drive belt fromslackening at depressions, when the rear end of the frame extensionrises.

It is advantageous if the limiting organs are two wheels rotating freelyon each side of the frame around the same horizontal axis.

The frame extension according to the invention together with theoriginal sledge form .one entity which follows the ground. Even atabrupt depressions the front part of the sledge rises easily uphill. Thesteerability of such a sledge is also good since, when tilted, theflexible frame tends to assimilate to the sharpness of the curve. As theframe follows the ground, the entire length of the lengthened drive beltgets a good grip of the ground and the pulling efficiencyis good in allpositions because of the limiting organs. This is also why the sledgeruns very well in soft snow, which was particularly noticeable in steepuphill tests in which it was compared with fixed frame extensions.Because of the ladder structure, the hinging, and the springing, a frameextension according to the invention can be constructed with smallmaterial thickness without decreasing the durability. In this case theweight of the frame extension remains as small as possible and thesurface pressure of the lengthened drive belt considerably smaller thanthat in the previously known solutions.

DESCRIPTION OF THE DRAWINGS FIG. 1 shows a perspective view of the frameextension,

2 FIG. 2 shows the mounting scheme for the same frame-extension, and

FIG. 3 shows a motor sledge according to the invention at difl'erentground positions.

DESCRIPTION OF THE PREF ERRED EMBODIMENT cording to the drawing, withthe extension frame is attached to the sledge frame by screws, havebeenfattached to the same axle by branch cotters. One set of wheels 6has been attached by screws 5 to lobes 4. The frame extension has beenfittedl at the axle of the wheels by spiral springs 7 provided with'pins to the lobes welded to the lift bow of the sledge. The back axlewheels 8 have been sprung with swinging arms 9 and attached to the frameshafts by extensions 10 fitted inside the shaft. The ends of the axle ofthe limiting rolls ll of the drive belt have been attached by screws atthe hinging of the frame extension to the frame of the sledge above thedrive belt. The limiting rolls prevent, I

tension to its lowest position. The stiffness of the flexibility can beeasily regulated according to the ground, r

the snow conditions, and the weight of the driver or the load to becarried by control plates to be added to the ends of the spiral springs.

When a frame longer than the frame extension according to the inventionis desired, it can be obtained a by extending the frame shafts tocorrespond with the desired number of wheels.

The frame extension can be hinged to the sledge, frame even without theattachment pieces 3 that elevate the frame. In this case the ability ofthe frame extension to bend upwards, however, decreases when the innerspace of the frame lowers. The frame extension can also be hinged to aseparate axle behind the hindmost roller wheelsof the sledge.

With different applications an extension according to the inventionsuits most known sledge brands in which the motor is in the front of thesledge. A frame extension according to the invention can also be fittedto motor sledges with two belts.

What is claimed is:

1. An improved motor sledge of the type having a rigid frameconstruction; steering means attached to the front part of the frameconstruction for pivotable movement around a substantially verticalaxis; a plurality of wheels rotatably mounted under the frameconstruction; a supplementary frame portion attached to the rear end ofthe frame construction for flexible pivotable movement around ahorizontal axis therein and further provided with wheels; at least onecommon endless drive belt fitted around the wheels; a power 3 sourcefixed to the frame construction; and power ing.

2. The improved motor sledgeof claim 1, in which the means forpreventing slackening of the drive belt comprise a pair of coaxial rollsrotatably mounted on opposite sides of the frame construction forpreventing a pair of drive belts from slackening.

wards in order to prevent the drive belt from slacken-

1. An improved motor sledge of the type having a rigid frameconstruction; steering means attached to the front part of the frameconstruction for pivotable movement around a substantially verticalaxis; a plurality of wheels rotatably mounted under the frameconstruction; a supplementary frame portion attached to the rear end ofthe frame construction for flexible pivotable movement around ahorizontal axis therein and further provided with wheels; at least onecommon endless drive belt fitted around the wheels; a power source fixedto the frame construction; and power transmission means connected to thepower source for moving the drive belt, wherein the improvementcomprises: means attached to the rear end of the frame constructionsubstantially above the horizontal axis to be pressed against the uppersurface of the drive belt whenever the supplementary frame portionpivots upwards in order to prevent the drive belt from slackening. 2.The improved motor sledge of claim 1, in which the means for preventingslackening of the drive belt comprise a pair of coaxial rolls rotatablymounted on opposite sides of the frame construction for preventing apair of drive belts from slackening.